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CVE-2026-88771: Citrix NetScaler Improper Input Validation Vulnerability

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CRITICAL 9.8EXPLOITEDREMOTEUPGRADEUPGRADE

CVE-2026-88771 is a critical-severity flaw (CVSS 9.8) affecting netscaler application delivery controller, netscaler gateway, reported as exploited in the wild. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Improper input validation vulnerability in Citrix NetScaler ADC and Citrix NetScaler Gateway. This issue affects ADC: before 14.1-73.37, before 13.1-64.23, before 14.1-73.37 FIPS, and before 13.1.37.279 FIPS and NDcPP; Gateway: before 14.1-73.37 and before 13.1-64.23 leading to an unauthenticated attacker to execute arbitrary commands.

Why this priority

  • Critical severity
  • EPSS top 8%: very likely to be exploited
  • Exploited in the wild (CISA KEV)
  • Public exploit reference
  • Covered by 5 security sources
  • CISA SSVC: automatable with total technical impact
  • Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score9.8 (Critical)
Attack vectorNetwork (remote)
Attack complexityLow
Privileges neededNone
User interactionNone
EPSS exploit chance4.7% (top 8%)
CISA exploited listYes, fix due 2026-09-30
WeaknessCWE-20
Published2026-09-27
Last modified2026-09-29
Publisher (CNA): NetScaler · Vendor: citrix

Am I affected?

Timeline

citrix netscaler application delivery controller UPGRADE
Affected: >= 13.1 and < 13.1-64.23 · >= 13.1 and < 13.1.37.279 · >= 14.1 and < 14.1-73.37 · >= 14.1-66.68 and <= 14.1-73.37
Fixed in: 13.1.37.279, 13.1-64.23, 14.1-73.37
Safe to downgrade to: a release before 13.1
1. Check installed version
apt-cache policy netscaler-application-delivery-controller || rpm -q netscaler-application-delivery-controller || netscaler-application-delivery-controller --version
2. UPGRADE to 13.1.37.279 (Debian / Ubuntu)
sudo apt update && sudo apt install --only-upgrade netscaler-application-delivery-controller
2. UPGRADE (RHEL / Amazon Linux / Fedora)
sudo dnf upgrade netscaler-application-delivery-controller
Note
Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.
3. If no update is available yet, DOWNGRADE to a release before 13.1 (Debian / Ubuntu)
apt-cache madison netscaler-application-delivery-controller sudo apt install netscaler-application-delivery-controller=<VERSION_BEFORE_13.1> sudo apt-mark hold netscaler-application-delivery-controller
3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)
dnf --showduplicates list netscaler-application-delivery-controller sudo dnf downgrade netscaler-application-delivery-controller-<VERSION_BEFORE_13.1> sudo dnf versionlock add netscaler-application-delivery-controller
Downgrade risk
Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.
After downgrade
Restart the service, and keep the package held until a fixed release ships.
citrix netscaler gateway UPGRADE
Affected: >= 13.1 and < 13.1-64.23 · >= 14.1 and < 14.1-73.37
Fixed in: 13.1-64.23, 14.1-73.37
Safe to downgrade to: a release before 13.1
1. Check installed version
apt-cache policy netscaler-gateway || rpm -q netscaler-gateway || netscaler-gateway --version
2. UPGRADE to 13.1-64.23 (Debian / Ubuntu)
sudo apt update && sudo apt install --only-upgrade netscaler-gateway
2. UPGRADE (RHEL / Amazon Linux / Fedora)
sudo dnf upgrade netscaler-gateway
Note
Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.
3. If no update is available yet, DOWNGRADE to a release before 13.1 (Debian / Ubuntu)
apt-cache madison netscaler-gateway sudo apt install netscaler-gateway=<VERSION_BEFORE_13.1> sudo apt-mark hold netscaler-gateway
3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)
dnf --showduplicates list netscaler-gateway sudo dnf downgrade netscaler-gateway-<VERSION_BEFORE_13.1> sudo dnf versionlock add netscaler-gateway
Downgrade risk
Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.
After downgrade
Restart the service, and keep the package held until a fixed release ships.

Exact fixes by distribution

Fedora 46 · uv · FIXED · 0.13.5-1.fc46 · FEDORA-2026-61ea5a28c6 · source
sudo dnf upgrade --advisory=FEDORA-2026-61ea5a28c6

Public exploits and detection

Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.

Advisories and coverage

Research and news

Verify at the official source NVD · CVE Program · CISA KEV catalog · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Related CVEs

References

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